Products obtained by dimerization of conjugated dienes and further hydrogenation may be used in different fields, such as flavors and fragrances, pharmaceutical, cosmetics, solvents and lubricants applications. in cosmetic applications, hydrogenated dimers obtained from conjugated dienes may be used in creams, such as nutrient creams and medicated creams or in toilet or milky lotion, in lipstick or in face powder. In pharmaceutical applications, hydrogenated dimers obtained from conjugated dienes may be used in medical and pharmaceutical preparations such as ointments, and medical lubricating agents. as an example of a useful hydrogenated dimer, special mention can be made to squalane, isosqualane and crocetane, obtained respectively by hydrogenation of squalene, isosqualene and crocetene.
The dimerization process of conjugated dienes is generally performed using a catalyst in the presence of a solvent. U.S. Pat. No. 8,669,403 describes the dimerization of farnesene using 2-propanol as solvent. Document WO 2011/146837 describes processes for catalytic dimerization of farnesene, said processes can be carried out in a protic solvent, such as a primary or a secondary alcohol, such as isopropanol. The protic solvents are very expensive and are thus not convenient for an industrial process. There still exists a need for the dimerization of conjugated dienes by an industrial process which would be economical and would present an improved yield and/or selectivity for the desired dimers.
Document GB 1,061,482 describes the dimerization of 1,3-butadiene in the presence of a solvent and a high amount of phenol. However, this document is silent on the issue of preparing selectively head-to-head dimers.